In the fabrication of so-called composites for use in the aircraft and aerospace industry, tooling and assembly costs are major drivers. Conventional tooling for the fabrication of composites generally has a fixed geometry and is very costly to manufacture. Additionally, such current tooling may have short lifetimes and demonstrate inappropriate shrinking characteristics.
Aluminum is the most popular tooling material for low volume production, up to 100 parts, whereas steel is the first choice for volumes over about 100 parts. For the creation of master patterns, plaster is the most popular material followed by wood, modeling board and aluminum. Invar (iron-nickel) has been used to some extent in the aerospace industry because of a good match of thermal expansion coefficients with those of graphite/epoxy materials. This tooling material is, however, very expensive and requires significant lead times for machining. As a result, significant effort has been applied in developing CAD software to reduce the time needed for tooling design to shorten the overall prototype or product fabrication cycle. To the best of our knowledge, there have been no breakthroughs in tooling materials, techniques or approaches in the last decade.
The above problems are especially acute in the fabrication of mandrels. Commonly used techniques for the fabrication of this tooling include the use of: nylon bagged styrofoam cores; solid metal mandrels; soft inflatable bladders; hollow silicone mandrels; thermoplastic mandrels; machined foam flyaway; and water soluble substances such as eutectic salts. In the use of such systems, depending upon that used, demolding and materials costs are significant problems. As a consequence, most mandrels are machined from solid pieces of material such as aluminum or cast into a fixed shape and cannot be easily reconfigured.
Accordingly, the availability of relatively low cost tooling that is reconfigurable and readily and cheaply fabricated would be of significant value to the aircraft and aerospace industries in the fabrication of composite structures.